Sun blinds using for example a cellular or pleated single sheet material for covering windows are known in the art. It is usually a simple matter to mount such cross-sectionally shaped material to a headrail when the opening to be covered is rectangular. The headrail merely captures the uppermost cell, pleat, or flaps formed thereon. The headrail extends parallel to the cells or pleats and permits any number of attachment techniques.
However, when the opening to be covered is trapezoidal or has a slanted top edge, the method of retaining the fabric becomes more complicated. This is due in part to the fact that the cells or pleats of the blind that contact the headrail are of different lengths and usually terminate with an open or free end at the rail. Thus, the attachment device must be capable of easy connection and infinite adjustment of angle of attachment.